Over 10 million Americans suffer from chronic kidney disease and kidney cancer, resulting in 109,000 deaths a year and disability to many times that number. Better methods to study renal function and detect and accurately diagnose pathology are needed. Imaging is important to urology and nephrology, and improved functional kidney imaging could improve health care by enabling image guided diagnoses, procedures, therapies, and monitoring. Unfortunately, all of the x-ray contrast agents (which are based on iodine) are nephrotoxic, and a FDA warning has been issued discouraging use of gadolinium MRI imaging for persons with decreased renal function, thus limiting the important usefulness of CT and MRI. We have found that small gold nanoparticles produce excellent radiographic imaging of blood vessels and are rapidly filtered by the kidneys into the bladder thus producing exquisite imaging of the urinary system. Initial toxicity tests show them to be non-toxic at useful levels. These agents have a completely different chemistry from iodine and gadolinium agents and may be able to fill the void in noninvasive high resolution imaging of the urinary system. Preliminary tests have shown unsurpassed high resolution functional kidney imaging. In the work proposed, gold nanoparticles will be optimized and their safety evaluated in compromised kidneys compared to iodine agents in mice. Detection of acute tubular necrosis will be demonstrated using microCT. If this work is successful, these novel contrast agents could lead to earlier and more accurate detection of renal pathology with concomitant improved treatments and outcomes for many patients. Relevance to Public Health: We have recently developed new agents to better image kidney function using nanotechnology. If this study is successful, these novel agents could lead to earlier and more accurate detection of kidney disorders resulting in improved treatments and outcomes for many patients. [unreadable] [unreadable] [unreadable]